BANGKOK (Reuters) - Thailand's King Bhumibol Adulyadej canceled a public appearance on his 87th birthday on Friday on the advice of doctors, disappointing thousands camped outside the hospital hoping for a glimpse of the world's longest-reigning monarch.
The cancellation fuels mounting concern over the health of King Bhumibol, a god-like figure for many and widely seen as a unifying figure through years of political unrest.
It also comes at a sensitive time for the Southeast Asian nation, six months after the army took over in a coup and amid a widening corruption investigation that has led to the arrest of relatives of Princess Srirasmi, the wife of the Crown Prince.
The king's birthday is also known as "Father's Day" in Thailand and is a public holiday.
King Bhumibol was admitted to Bangkok's Siriraj Hospital in October and underwent an operation to remove his gallbladder.
"A team of royal physicians ... agreed that he is not ready to grant a royal audience and therefore doctors have recommended he cancel royal activities," the Royal Household Bureau said in a statement.
The king last appeared in public in November.
Thousands gathered at the hospital after hearing the news, with most wearing yellow, a color associated with the monarchy. Some shouted "long live the king" and waved yellow flags while others held portraits.
"It doesn't matter whether he appears in public or not," said Thepwitoon Chim-ngog, 37. "I'm just happy that I'm here to show my loyalty to him."
King Bhumibol's health and anxiety over the succession have formed part of the backdrop to a complex crisis driven by Thailand's rival business and political elite.
King Bhumibol, also known as Rama IX, carries considerable moral weight in Thailand. The king has in the past used birthday speeches to comment on the state of the nation or, as in 2001 with then Prime Minister Thaksin Shinawatra, to criticize government leaders.
The king made several interventions in the 1970s and 1990s to call for calm during political upheaval. He was silent during the latest crisis, which began in November and culminated in the May 22 coup.
The military government of Prime Minister Prayuth Chan-ocha, a staunch royalist, has called on all Thais to wear yellow throughout December to mark the monarch's birthday.
Crown Prince Maha Vajiralongkorn, the king's only son, is expected to carry out official ceremonies to mark his father's birthday.
(Reporting by Juarawee Kittisilpa and Viparat Jantraprapaweth; Writing by Amy Sawitta Lefevre; Editing by Nick Macfie)